"The FBI is taking this very seriously. They were at our office for about an hour today, and they tell us that they're running down some leads," Jesse Benton, the Kentucky Republican's campaign manager, told radio host Mike Huckabee on his show on Wednesday.

Benton likened the alleged incident to "Gestapo ... scare tactics."

The meeting with the FBI took place at the senator's Louisville, Ky., campaign headquarters, where information was handed over to agency officials, a source close to the campaign confirmed.

McConnell's campaign had called Tuesday for a probe into an audiotape published by liberal news website Mother Jones. The tape, made in February, included McConnell, top strategists and senior staff discussing the senator's re-election campaign and potential challenger Democratic actress Ashley Judd. On it, McConnell and staff discuss using Judd's history of depression as well as her views on religion against her. Judd decided on March 27 not to run.

Mother Jones said in a statement that it was recently provided the tape by an anonymous source: "We were not involved in the making of the tape, but we published a story on the tape due to its obvious newsworthiness. It is our understanding that the tape was not the product of a Watergate-style bugging operation. We cannot comment beyond that."

But McConnell's camp believes the meeting was bugged as part of a political attack from the left.

"I can say with the utmost certainty that this did not come from anybody inside of our campaign," Benton told Huckabee. "So, that could only lead us to believe that this was illegally and illicitly recorded by an outside source, which is felonious and unethical and immoral."